tests: add ProviderHelperSaveTest, with long key id collision test

OpenKeychain/src/main/java/org/sufficientlysecure/keychain/provider/KeychainDatabase.java

@@ -349,4 +349,9 @@ public class KeychainDatabase extends SQLiteOpenHelper {
         copy(in, out);
     }
 
+    // for test cases ONLY!!
+    public void clearDatabase() {
+        getWritableDatabase().execSQL("delete from " + Tables.KEY_RINGS_PUBLIC);
+    }
+
 }